The placenta is a frisbee shaped wonder pack. It has lots of jobs to do when you are growing a baby. BUT in 1 in 200 pregnancies it can get in the way of the baby making its way out of the cervix.
Brigid: The placenta has been in the news in the last couple of years because of celebrities endorsing eating their placenta after birth which can be a topic for another day.
If you are interested to find more out about that than just drop us an email at firstname.lastname@example.org
But other than that, we'll just talk about the positioning of the placenta in this one.
Okay so Dr. Pat can you describe the placenta to our listeners as we don't often talk about the placenta!
Patrick [00:01:10] The placenta is that structure that that sits on the interior aspect of the uterus. Attached to the placenta is the cord and it's the interface between the growing baby and the mother. It's got lots of jobs. So the main one is to send oxygen and nutrients from the mother's circulation down the cord into the baby and to send some foetal waste products back up the cord into the placenta and off around the mother's body for excretion. So it also is a it's a gland that makes it makes hormones as well.
Brigid [00:01:48] Wow I didn't know that. What though?
Patrick [00:01:50] The pregnancy hormone progesterone, some of that is made by the placenta as well.
Brigid [00:01:57] I thought that wasn't its role so that's a surprise. So what happens to the placenta as the baby grows?
Patrick [00:02:04] Well the placenta as you know, it starts off really really small. When that fertilized egg first starts to implant in the urine lining there isn't a placenta yet. In the early weeks of the pregnancy it forms as a separate structure and then just gets bigger and bigger as the as the pregnancy progresses. And some of the abnormalities that can happen in pregnancy are when things that happen when the process of forming a placenta which is called Placentation doesn't doesn't happen properly.
Brigid [00:02:35] Right. And so when we go for our 18 to 20 week scan which is really, it's fun that 18 to 20 week scan you don't get the full picture of the baby but you get bits of the baby and you can see little hands in good detail and feet in good detail and and other things such as what sex the baby is. So we actually have done a really great episode and we in the GrowMyBaby program where we talk about what to expect during the 20 week ultrasound.
Patrick [00:03:02] You know what to expect and what what they're looking for. And of course what the family members who are there and the woman herself might be looking for is those happy snaps and that the baby's looking like a proper person by now.
Patrick [00:03:13] But on the obstetrician side we're also looking to exclude abnormalities in the placenta as part of that. So we want to make sure the placenta is in the right place i.e. not covering the opening the top of the vagina of the cervix and blocking the baby's passage out so when labour comes and also the placenta looks like its normal size that it doesn't have one of the unusual or abnormal placental shapes and that the cord inserts into the placenta at a normal spot. All of those things are quite relevant to how well the rest of the pregnancy is kind of progressed.
Brigid [00:03:52] And so when you say you're looking at the placenta's position. So the placenta has different positions within the uterus.
Patrick [00:03:58] Yeah it can be anywhere. It could sit anywhere within the within the growing uterus and just about all the positions are normal except the one where it's sitting right over the top of the vagina. Yeah. So there's a condition called placenta praevia which is what we're looking for and that's the placenta in that in that bad position. And then there's a sort of a borderline placenta praevia where it's close to the cervix. And that woman will be then be re scanned at 30-32 for weeks to make sure it's moved out of the way.
Brigid [00:04:28] I'm going to ask a probably obvious question but it's not a floating structure is it not.
Patrick [00:04:33] It doesn't float, it's attached to the uterus so it doesn't actually move. That's a that's a misnomer - it doesn't actually move. What happens is that if it's right down near the cervix the bit of the uterus that's between the placenta and the cervix expands in late pregnancy that it's called the lower segment that's the last bit to expand and it's the bit where the head will wind up right at the end of the pregnancy and as the lowest segment forms that has the effect of appearing to move the placenta upwards. But it's not actually floating around it's attached to the uterus and attached early.
Brigid [00:05:15] So how common is it for the placenta to completely cover the uterus.
Patrick [00:05:20] About one in two hundred and that's you know that's a lot isn't it. Yeah for a condition that that prior to the invention of modern obstetrics would was presumably universally catastrophic for mother and baby So it must be one of the reasons why it used to be dangerous to have a baby.
Patrick [00:05:38] And identifying placenta praevia it was sort of the crowning glory of the early days of ultrasound. So really decent people I know really decent ultrasounds where I can actually see much. It's only about 40 years old so the the ultrasounds even from back then were pretty clumsy images compared to what we can see now. Yeah but reliable identification of placenta praevia was was one of the first things that they know when ultrasound was was developed because it's easy to see.
Patrick [00:06:11] And then later on they used it for all the millions of other things that fantastic for you.
Brigid [00:06:14] Do you have any say over where your placenta is positioned in?
Patrick [00:06:19] That's that's just sort of bad luck. There's nothing you can do about that it's just where the placenta forms. A proper placenta praevia where it's covering the opening. That's not a treatable thing. Can't move it. Yeah. What we do in a situation of placenta preview is observe that woman closely because what we call a major placenta praevia is where it's really covering the opening is also a sort of is also associated with growth restriction. So a placenta in that position is not just blocking that way out but it's also at risk of not working properly.
Patrick [00:06:48] So that one will be watched closely for the baby's growing appropriately and then a plan is to be made for a caesarean section.
Brigid [00:06:55] Yeah right. Because vaginal birth is completely off the table?
Patrick [00:06:58] Absolutely. If it's a major praevia if it's one of those borderline ones then it's possible in labour for the head to sneak past the placenta. Yeah.
Patrick [00:07:07] And the baby to be born vaginally but again a watch that labour closely.
Brigid [00:07:12] So at the 18 to 20 week scan where the placenta is it's been identified that it's covering the cervix what's the normal sort of progression for that person.
Patrick [00:07:25] Well that that we would do those extra some extra care to make sure that the baby was growing properly and then at 32 to 34 weeks we have another look. So what the placenta was doing and if it's still covering the cervix at that late stage then the plans would be made for a caesarean section.
Brigid [00:07:41] Early. Like is that person going to get to full term?
Patrick [00:07:44] No you don't really want them to get to full term because you really don't want that woman to labour, at all really. That could be dangerous and associated with heavy bleeding so remember the cervix when it comes to labour the cervix softens. And then it shortens and then it dilates and we don't really want any of those things to happen. So a section would be set up for that woman in the third trimester but you know late in the third trimester but not so late that she might come into labour. And what someone with a placenta praevia might experience throughout the pregnancy, a major placenta praevia might experience throughout the pregnancy is lots of multiple episodes of bleeding.
Brigid [00:08:20] Right throughout the pregnancy from say about 20 weeks?
Patrick [00:08:23] Yeah. It doesn't always happen. Yeah but it certainly certainly can and it's sometimes the thing that brings up wasn't appropriate to our attention.
Brigid [00:08:30] This is a story that a friend told me the other day at the school drop off and then we get lots of stories that point yet. Yeah. And she was telling me about her friend who who definitely had that sort of bleeding throughout her pregnancy because of placenta praevia. And she was told to have pelvic rest for the rest of her pregnancy. That just means no sex right?
Patrick [00:08:48] I guess I guess I don't know what pelvic rest is I. We're all using our pelvis at all times aren't we? I think I guess it means no sex. I think that there will definitely be a phenomenon of bleeding from placenta praevia being provoked by sex whether or not that's harmful. It's hard to say but it would kill the mood. So you know I think that that it would be you know be quite common for people to be advised not to have sex if it's causing bleeding. Placenta praevia a different situation to just the odd little bleed that can happen in pregnancy where we do a scan, can't find the source of the bleed, baby looks fine carry on. Yeah but bleeding from placenta praevia can be tricky and it can be heavy so that once upon a time women with major praevia were admitted to the hospital bed rest for the whole thing. Yeah well yeah. And like a lot of the things that they used to admit women to hospital for right throughout the pregnancy didn't work. The bed the bed rest didn't work.
Brigid [00:09:50] Okay. Still ended up with the same outcome?
Patrick [00:09:52] Yeah it didn't really change much. They probably gave some women DVT from putting me into bed for twelve weeks.
Brigid [00:09:59] Now a DVT?
Patrick [00:09:59] A DVT is a deep venous thrombosis a blood clot in your leg that you might get for sitting around in bed, inactivity. Yeah but it didn't seem to change outcomes so the usual thing that's done with placenta praevia now is that if you've been identified with the placenta praevia but you're not bleeding then you managed in the community at your house and you come in the visits with you care providers like everybody else. If you bleed from a placenta praevia we tend to admit those women just because a small bleed can be a warning that a bigger bleed is coming.
Patrick [00:10:31] So we might admit that woman to the hospital for a few days. Yes. Just to observe. And so she's there with us.
Patrick [00:10:39] If a big bleed happens and she could be transfused or delivered or whatever was needed. And then if nothing bad happens in the few days since she can go home again.
Brigid [00:10:49] Yeah. So if you've had one pregnancy with placenta previous Are you likely to have another one?
Patrick [00:10:55] Yeah I think the data suggests that that you are slightly more likely to have another one if you've had one that is that there might be people who are just a bit somehow prone to it. I certainly don't understand exactly how that works. But I think I think having a previous praevia is a risk factor. But you know the second trimester ultrasound is going to find that we'll know anyway.
Brigid [00:11:16] Yeah. And what about family histories. Is it inherited?
Patrick [00:11:21] I don't exactly know. No I don't think so. I mean prior to the invention of safe caesarean sections, which isn't that old, most people with major praevia would have died. So therefore they wouldn't have lived to pass that genetic trait down. Yeah.
Brigid [00:11:37] All right. So just to recap so people aren't panicking. 1 in 200 pregnancies have placenta praevia. The things that we're looking out for bleeds. It will be diagnosed in your 20 week scan and if you're just all at all concerned you have to speak to your care provider.
Patrick [00:11:58] Absolutely. So the whilst no one's pleased to hear the placenta praevia this is this is something that modern obstetrics has has really got handled. And again it's may not be ideal to a lot of people to need to have a baby by Caesarean section but if you've had a Caesarean section for your first baby because of placenta praevia, then providing you don't have placenta preview again. There's no reason why you can't have a VBAC which is vaginal birth after caesarean for the second, third, fourth, fifth baby.
Brigid [00:12:29] Yeah. And we love fifth babies don't we?
Patrick [00:12:31] Yeah not enough people have five babies. 😊
Brigid [00:12:34] Good. All right. Well that's the end of this episode about everything about the placenta position and if you're interested in finding out about their GrowMyBaby program then jump on over to our website.
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